text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef UI_GL_GL_CONTEXT_H_
  #define UI_GL_GL_CONTEXT_H_
  
  #include <string>
  #include <vector>
  
  #include "base/basictypes.h"
  #include "base/memory/ref_counted.h"
  #include "base/memory/scoped_ptr.h"
  #include "base/synchronization/cancellation_flag.h"
  #include "ui/gl/gl_share_group.h"
  #include "ui/gl/gl_state_restorer.h"
  #include "ui/gl/gpu_preference.h"
  
  namespace gfx {
  
  class GLSurface;
  class VirtualGLApi;
  struct GLVersionInfo;
  
  // Encapsulates an OpenGL context, hiding platform specific management.
  class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
   public:
    explicit GLContext(GLShareGroup* share_group);
  
    // Initializes the GL context to be compatible with the given surface. The GL
    // context can be made with other surface's of the same type. The compatible
    // surface is only needed for certain platforms like WGL, OSMesa and GLX. It
    // should be specific for all platforms though.
    virtual bool Initialize(
        GLSurface* compatible_surface, GpuPreference gpu_preference) = 0;
  
    class FlushEvent : public base::RefCountedThreadSafe<FlushEvent> {
      public:
        bool IsSignaled();
  
      private:
        friend class base::RefCountedThreadSafe<FlushEvent>;
        friend class GLContext;
        FlushEvent();
        virtual ~FlushEvent();
        void Signal();
  
        base::CancellationFlag flag_;
    };
  
    // Needs to be called with this context current. It will return a FlushEvent
    // that is initially unsignaled, but will transition to signaled after the
    // next glFlush() or glFinish() occurs in this context.
    scoped_refptr<FlushEvent> SignalFlush();
  
    // Destroys the GL context.
    virtual void Destroy() = 0;
  
    // Makes the GL context and a surface current on the current thread.
    virtual bool MakeCurrent(GLSurface* surface) = 0;
  
    // Releases this GL context and surface as current on the current thread.
    virtual void ReleaseCurrent(GLSurface* surface) = 0;
  
    // Returns true if this context and surface is current. Pass a null surface
    // if the current surface is not important.
    virtual bool IsCurrent(GLSurface* surface) = 0;
  
    // Get the underlying platform specific GL context "handle".
    virtual void* GetHandle() = 0;
  
    // Gets the GLStateRestorer for the context.
    GLStateRestorer* GetGLStateRestorer();
  
    // Sets the GLStateRestorer for the context (takes ownership).
    void SetGLStateRestorer(GLStateRestorer* state_restorer);
  
    // Set swap interval. This context must be current.
    virtual void SetSwapInterval(int interval) = 0;
  
    // Returns space separated list of extensions. The context must be current.
    virtual std::string GetExtensions();
  
    // Returns in bytes the total amount of GPU memory for the GPU which this
    // context is currently rendering on. Returns false if no extension exists
    // to get the exact amount of GPU memory.
    virtual bool GetTotalGpuMemory(size_t* bytes);
  
    // Indicate that it is safe to force this context to switch GPUs, since
    // transitioning can cause corruption and hangs (OS X only).
    virtual void SetSafeToForceGpuSwitch();
  
    // Attempt to force the context to move to the GPU of its sharegroup. Return
    // false only in the event of an unexpected error on the context.
    virtual bool ForceGpuSwitchIfNeeded();
  
    // Indicate that the real context switches should unbind the FBO first
    // (For an Android work-around only).
    virtual void SetUnbindFboOnMakeCurrent();
  
    // Returns whether the current context supports the named extension. The
    // context must be current.
    bool HasExtension(const char* name);
  
    // Returns version info of the underlying GL context. The context must be
    // current.
    const GLVersionInfo* GetVersionInfo();
  
    GLShareGroup* share_group();
  
    // Create a GL context that is compatible with the given surface.
    // |share_group|, if non-NULL, is a group of contexts which the
    // internally created OpenGL context shares textures and other resources.
    static scoped_refptr<GLContext> CreateGLContext(
        GLShareGroup* share_group,
        GLSurface* compatible_surface,
        GpuPreference gpu_preference);
  
    static bool LosesAllContextsOnContextLost();
  
    // Returns the last GLContext made current, virtual or real.
    static GLContext* GetCurrent();
  
    virtual bool WasAllocatedUsingRobustnessExtension();
  
    // Use this context for virtualization.
    void SetupForVirtualization();
  
    // Make this context current when used for context virtualization.
    bool MakeVirtuallyCurrent(GLContext* virtual_context, GLSurface* surface);
  
    // Notify this context that |virtual_context|, that was using us, is
    // being released or destroyed.
    void OnReleaseVirtuallyCurrent(GLContext* virtual_context);
  
    // Returns the GL version string. The context must be current.
    virtual std::string GetGLVersion();
  
    // Returns the GL renderer string. The context must be current.
    virtual std::string GetGLRenderer();
  
    // Called when glFlush()/glFinish() is called with this context current.
    void OnFlush();
  
   protected:
    virtual ~GLContext();
  
    // Will release the current context when going out of scope, unless canceled.
    class ScopedReleaseCurrent {
     public:
      ScopedReleaseCurrent();
      ~ScopedReleaseCurrent();
  
      void Cancel();
  
     private:
      bool canceled_;
    };
  
    // Sets the GL api to the real hardware API (vs the VirtualAPI)
    static void SetRealGLApi();
    virtual void SetCurrent(GLSurface* surface);
  
    // Initialize function pointers to functions where the bound version depends
    // on GL version or supported extensions. Should be called immediately after
    // this context is made current.
    bool InitializeDynamicBindings();
  
    // Returns the last real (non-virtual) GLContext made current.
    static GLContext* GetRealCurrent();
  
   private:
    friend class base::RefCounted<GLContext>;
  
    // For GetRealCurrent.
    friend class VirtualGLApi;
  
    scoped_refptr<GLShareGroup> share_group_;
    scoped_ptr<VirtualGLApi> virtual_gl_api_;
    scoped_ptr<GLStateRestorer> state_restorer_;
    scoped_ptr<GLVersionInfo> version_info_;
  
    std::vector<scoped_refptr<FlushEvent> > flush_events_;
  
    DISALLOW_COPY_AND_ASSIGN(GLContext);
  };
  
  class GL_EXPORT GLContextReal : public GLContext {
   public:
    explicit GLContextReal(GLShareGroup* share_group);
  
   protected:
    ~GLContextReal() override;
  
    void SetCurrent(GLSurface* surface) override;
  
   private:
    DISALLOW_COPY_AND_ASSIGN(GLContextReal);
  };
  
  }  // namespace gfx
  
  #endif  // UI_GL_GL_CONTEXT_H_
  